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Friday, October 12, 2012

Finnish diet? No thanks!: Diet and health

There were two stories about stroke on yesterday's BBC website, one warning that incidence is rising among younger people and the other that tomatoes are protective. Both are from studies published in the October Neurology, the first a study of a region in Ohio with a population of 1.3 million, in which incidence was ascertained for 2 different periods, July 1993- June 1994 and 1999-2005. Mean age at stroke decreased from 71.2 years in 1993/4 to 69.2 in the later period, with the proportion occurring in people under age 55 increasing from 12.9% in 1993/4 to 18.6% in 2005.

This is alarming, says the paper and the BBC story, because stroke in younger people can mean more years of debilitation. But, did they find that incidence is actually increasing in younger people, or is it that incidence is decreasing in older people? It turns out that it's both. Stroke has risen from 109 per 100,000 people in 1993/4 to 176 per 100,000 in 2005, and the rate has fallen in those in the oldest age groups.

This change could be real or, cautions a neurologist from University College London, it's possible that the way stroke was detected during the study has changed, and could explain some of the increase. Younger people might have been more likely to have the more reliable diagnostic scans.

A spokesperson from the Stroke Association in the UK said that while these results are alarming, stroke can be prevented. "For example, eating a balanced diet, exercising regularly and getting your blood pressure checked can all make a huge difference."

Or, just eat more tomatoes? The second study also appears in Neurology and reports that people with the highest levels of lycopene in their blood were the least likely to have a stroke -- lycopene is a compound found in tomatoes.

But, hold on.

The study involved 1,031 men in Finland between the ages of 46 and 65.
The level of lycopene in their blood was tested at the start of the
study and they were followed for an average of 12 years. During that
time, 67 men had a stroke.

Among the men with the lowest levels of lycopene, 25 of 258 men had a
stroke. Among those with the highest levels of lycopene, 11 of 259 men
had a stroke. When researchers looked at just strokes due to blood
clots, the results were even stronger. Those with the highest levels of
lycopene were 59 percent less likely to have a stroke than those with
the lowest levels.

"This study adds to the evidence that a diet high in fruits and
vegetables is associated with a lower risk of stroke,” said study author
Jouni Karppi, PhD, of the University of Eastern Finland in Kuopio. “The
results support the recommendation that people get more than five
servings of fruits and vegetables a day, which would likely lead to a
major reduction in the number of strokes worldwide, according to
previous research.”

Hm, maybe, but the sample sizes are pretty small here. Sounds to us as though the a priori assumption is that eating fruits and vegetables prevents stroke, and that these two studies support that view. Maybe they do, and we certainly won't argue, but we'd need a lot more evidence than this if we didn't already believe it.

A more convincing twenty-year study ended not so long ago, in Eastern Finland where heart disease risk was as high or higher than anywhere else in the world. The study asked Finns to eat a 'Mediterranean' diet, which was high in vegetables and so on. Their heart disease risk was reduced, according to the report, by about 75%! The details and specific food elements, if it is anything specific, were not identified, but the switch to fruits and vegetables from animal fats, cheese and so on, was in general credited with the reduction in risk.

Then the investigators proposed that an Italian population should adopt the Finnish diet to 'square' out the study design and its ability to compare and isolate dietary elements. The Italians (smartly!) refused.

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